grasp.py 文件源码

def load_series(self, subject, series):
        min_freq = self.min_freq
        max_freq = self.max_freq
        key = (subject, series, min_freq, max_freq) 
        if key not in self._series_cache:
            while len(self._series_cache) > self.MAX_CACHE_SIZE:
                # Randomly throw away an item
                self._series_cache.popitem()    
            print("Loading", subject, series)
            data = read_csv(path(subject, series, "data"))
            # Filter here since it's slow and we don't want to filter multiple
            # times. `lfilter` is CAUSAL and thus doesn't violate the ban on future data.
            if (self.min_freq is None) or (self.min_freq == 0):
                print("Low pass filtering, f_h =", max_freq)
                b, a = butter_lowpass(max_freq, SAMPLE_RATE, FILTER_N)
            else:
                print("Band pass filtering, f_l =", min_freq, "f_h =", max_freq)
                b, a = butter_bandpass(min_freq, max_freq, SAMPLE_RATE, FILTER_N)                
            self._series_cache[key] = lfilter(b, a, data, axis=0)
        return self._series_cache[key]